chore: 将后端移动到 api/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/submission/management/commands/recalculate_scores.py

@@ -0,0 +1,27 @@
+from django.core.management.base import BaseCommand
+
+from submission.models import Submission
+
+
+class Command(BaseCommand):
+    help = "Recalculate score, raw_score, and zone for all rated submissions"
+
+    def add_arguments(self, parser):
+        parser.add_argument("--dry-run", action="store_true", help="Show what would change without saving")
+
+    def handle(self, *args, **options):
+        dry_run = options["dry_run"]
+        qs = Submission.objects.filter(ratings__isnull=False).distinct()
+        total = qs.count()
+        self.stdout.write(f"Found {total} rated submission(s).")
+
+        if dry_run:
+            self.stdout.write("Dry run — no changes made.")
+            return
+
+        for i, s in enumerate(qs, 1):
+            old_score = s.score
+            s.update_score()
+            self.stdout.write(f"[{i}/{total}] {s.user.username}/{s.task.title}: {old_score:.3f} → {s.score:.3f}  zone={s.zone}")
+
+        self.stdout.write(self.style.SUCCESS("Done."))